This invention relates to steam dealkylation reactions for producing benzene or its lower homologs by dealkylation of toluene and of other alkylbenzenes.
A number of catalysts have been proposed for the steam dealkylation of aromatic hydrocarbons, these catalysts containing a porous carrier and at least one metal deposited on the carrier. By way of examples, there can be mentioned:
USSR Patent specification No. 213 776, disclosing a catalyst containing rhodium, nickel and alumina; PA1 U.S. Pat. No. 3,595,932, disclosing a catalyst containing a noble metal of the platinum family (platinum, palladium, rhodium, iridium, ruthenium) on a carrier consisting of alumina or combinations of alumina with nickel or cobalt; PA1 U.S. Pat. No. 3,436,433, disclosing a catalyst containing alumina, an alkali metal, ferric oxide, rhodium and chromium; PA1 U.S. Pat. Nos. 3,649,706 and 3,649,707, disclosing catalysts containing mixtures of an alkali metal with ferric oxide, chromium and a metal selected from platinum, palladium and rhodium; PA1 U.S. Pat. No. 4,013,734, disclosing a catalyst containing alumina, a noble metal of the platinum family and a metal selected from vanadium, niobium and tantalum; PA1 French Pat. No. 2,317,962 to Cerciat and Szabo (equivalent to Ger. Pat. No. 2,629,647), disclosing a catalyst containing alumina and alumina-silicas in addition to rhodium and a metal from group IV A, particularly tin.
The catalysts used up to now suffer from a clearly insufficient stability, this lack of stability resulting in rapid deactivation and rapid mechanical disaggregation of the catalyst.